The AR-STONER(TM) 9mm Extended Heavy Buffer is perfect for your 9mm AR-15 Carbine. An extended heavy buffer shortens the length the bolt travels, slows the speed of the bolt during recoil and decreases the force exerted on the bolt catch. The steel construction provides outstanding durability and a wear resistant finish. Whether you are building a new 9mm AR-15 Carbine, or upgrading a rifle; the AR-STONER(TM) 9mm Extended Heavy Buffer is an excellent part for the price.